1. Field of the Invention
The present invention relates to a coolant supply method and apparatus for intercepting an air layer rotating to follow a grinding wheel end surface to supply coolant of a sufficient volume to a grinding point in a grinding machine which grinds an end surface of a workpiece with a grinding wheel end surface of the grinding wheel.
2. Discussion of the Related Art
In a grinding machine having a grinding wheel drivingly rotatably supported on a wheel head and a workpiece drivingly rotatably supported on a workpiece support device, it is often the case that the wheel head is advanced toward the workpiece support device with coolant being supplied to a grinding point so that both ends surfaces of the grinding wheel respectively grind both end surfaces of a ground portion taking the shape of a concave groove on the workpiece and the circumferential surface of the grinding wheel then grinds a cylindrical external surface of the workpiece. In this case, the rotation of the grinding wheel causes air layers rotate to follow the grinding wheel end surfaces, and the air layers obstruct the flows of the coolant along the grinding wheel end surfaces to make the coolant supply to grinding points insufficient. For this reason and due to the fact that contact areas increase at the grinding points where the grinding wheel end surfaces each being flat are brought into contact respectively with the workpiece end surfaces, each of the workpiece end surfaces would suffer grinding burns during the grinding operation.
Japanese unexamined, published patent application No. 2004-17265 (equivalent: U.S. Pat. No. 6,921,321) describes a device for intercepting air layers rotating to follow a grinding wheel. Referring now to the drawings of the Japanese application, in order to prevent air layers which rotate together with a grinding wheel G to follow both end surfaces 23a, 23b of the same from reaching grinding points, the device is constructed to obliquely eject air jets 29, 29 respectively toward both end surfaces 23a, 23b of the grinding wheel G, wherein each of the air jets 29, 29 is ejected from a point 26, which is on a grinding wheel circumferential edge on an upstream side of a corresponding grinding point P, along the chord of a small arc section 27 on the grinding wheel front side including the grinding point P. The device is also provided with an air interception plate 31 which faces the both end surfaces 23a, 23b of the grinding wheel G with a slight clearance therebetween.
Further, there has also been known a right-angle nozzle type device shown in FIG. 6 of the present application. In the right-angle nozzle type device, in order that air layers 40 rotating to follow both end surfaces of a grinding wheel G are intercepted for supplying coolants of a sufficient volume to grinding points where the both end surfaces respectively grind workpiece end surfaces, a pair of first nozzles 41 and a pair of second nozzles 42 are respectively arranged at first and second positions on the upstream side of the grinding points and are oriented to face the grinding wheel end surfaces at right angles, respectively.
In the wheel follow air layer intercepting device described in the aforementioned Japanese application, the position where the air interception plate 31 is mounted has to be far from the grinding points P to avoid the interference of the air interception plate 31 with the workpiece W, so that there cannot be attained a substantial effect of the air interception plate 31 in intercepting the air layers. Thus, the flow volume of each air jet 29 has to be increased for the substantial effect, thereby resulting in the massive air consumption.
In the aforementioned right-angle nozzle type device, it is intended to intercept the air layers 40 rotating to follow the grinding wheel end surfaces by the coolant flows which are ejected from the first and second nozzles 41, 42 at right angles toward the grinding wheel end surfaces and hence, to let the coolants cling onto the grinding wheel end surfaces. However, since the first and second nozzles eject the coolant flows toward the grinding wheel end surfaces at right angles, the splashing of the coolant wide spreads, and in addition, each coolant flow ejected toward the corresponding grinding wheel end surface at the second position adversely intercepts the coolant flow which has clung onto the corresponding grinding wheel end surface at the first position, so that the flow volume of the coolant rotating to follow each grinding wheel end surface becomes insufficient at the grinding point.